Piston



March 29, 1949. w VENNER ET AL 2,465,766

PISTON Filed Feb. 18, 1948 ATTORNEYS.

Patented Mar. 29, 1949 PISTON William M. Venner, Clayton, and Percy L.Bowser, Jr., University City, Mo.

Application February 18, 1948, Serial No. 9,086

Claims. (Cl. 30910) This invention pertains to pistons such as thelight-metal pistons used in internal-combustion engines for automobilesand the like.

Among other tendencies in the modern design of such engines onedevelopment has tended to increase the stroke of the piston. Theconsequences of such increase, where it is desired to avoid increase inthe over-all dimensions of the engine, may include shortening the pistonand increasing the angularity of the connecting rod. Each of thesechanges increases the tendency of the piston to rock in the cylinderabout the wristpin axis.

One of the objects of this invention is to provide an improved pistonhaving increased stability against such tendency to rock, and improvedcontrol of the fit of the piston in the cylinder.

Further objects will appear from the following description, taken inconnection with the accompanying drawings, in which will be set forth anillustrative embodiment of this invention. It is to be understood,however, that this invention is susceptible of various embodiments,Within the scope of the appended claims, with-out departing from theprinciples or spirit of the invention.

Generally stated, in accordance with this invention, the piston is soproportioned that the cylinder-bearing portion thereof extends wellabove the wrist-pin axis so that its support by the cylinder wall hasincreased leverage to resist the tendency to rock. This has beenaccompanied by shortening of the head portion and relocation of the slotor slots separating the thrust faces of the skirt from the head, andimproved means for sealing those slots have been .provided.

In the accompanying drawings,

Figure l is a side view, along the wrist-pin axis, of a piston embodyingthis invention, but without the sealing band,

Figure 2 is a half-section on line 22 of Figure 1,

Figure 3 is an enlarged, detail section taken on line 3-3 of Figure 2,but with the sealing band in place,

Figure 4 is a transverse section on line 4-4 of (fi re 2. also with thesealing band in place, an

Figure 5 includes side and edge views of the sealing band.

Referring to the drawings, I designates the skirt portion of the piston.This portion may be cam ground so as to be slightly smaller in diameterin the direction along the wrist-pin axis than in the directiontransverse thereto. The head portion 2 is defined by being considerablysmaller in diameter than the skirt portion I, so as to allow for maximumthermal expansion thereof without contacting the cylinder wall.Wrist-pin bosses 3 are spaced downward from the upper end of th skirtportion. Between the pin bosses and the upper end of the skirt portionone or more piston-ring grooves 4 may be formed, only one being shown inthe embodiment illustrated, leaving, between it and the upper end of theskirt portion a ring land 5 having the same size and shape incross-section as the skirt portion. Above the ring land 5, the headportion 2 is reduced in diameter as mentioned above to about .020 inchless than the skirt portion I. This is indicated, to exaggerated scale,at b in Figure 3. The head portion is also provided with one or morepiston-ring grooves B, and the skirt may have a bottom groove 7.

One or both thrust faces 8 of the skirt portion may be separated fromthe head portion by a horizontal slot or slots 9. This slot should beimmediately above the skirt portion. In the embodiment illustrated it islocated in the lowermost of the ring grooves 6. One or both thrust facesmay also be cut by a vertical slot l0 extending downward from the slot 9to render the thrust face more flexible.

In order to prevent leakage of the pressure fluid through the slots 9 tothe interior of the piston, a sealing band II is provided. This may be asimple ring of thin spring steel formed as shown in Figure 5 to adiameter a little less than that of the piston in the bottom of thegroove 6. This band is then simply snapped around the piston in thebottom of the groove 6, and so as to cover and seal the slot or slots 9.

The piston, constructed as decsribed above, may be made of alight metalsuch as aluminum, magnesium, or an alloy thereof, and the dimensionsreferred to may be adjusted to suit the rate of expansion of the metalused. Thus, the piston, when at its operating temperature, is fitted tothe cylinder to provide a bearing thereon which extends well abovewrist-pin axis and is, therefore, effective in preventing rocking of thepiston about that axis.

In order to control the thermal expansion of the thrust faces, a controlelement I2 may be provided. This may be made of steel or other materialhaving a rate of thermal expansion less than that of the piston metal,and is located within the piston and anchored to the thrust faces. Manytypes of control element may be used.

in shape, and anchored to the middle of one In the illustratedembodiment it is ovalthrust face, as at l3, and to the lateral portionsof the other, as at M. The action of a control element of this type isdisclosed in our -co-pending application Serial No. 787,276, filedNovember 21, 1947. Or it may be anchored at the middle points, as 13, ofboth faces. The action of such an element is disclosed in our co-pendingapplication Serial No. 719,842 filed January 2, 1947.

It has been found that this invention provides a piston which isrelatively stable against rocking about the wrist-pin axis. The skirtportion, extended upward from the wrist-pin bosses, provides a bearingagainst the cylinder wall above the pin axis effective to counteract theeffect of the connecting-rod thrust tending to tip the piston about saidaxis. While the axial length of the head portion may be reduced, thenumber of piston rings need not be reduced as one or more of them may beplaced on the skirt portion. While moving the slot 9 toward the head hasplaced it in a region of higher pressure of the pressure fluid, the bandI I provides an effective seal against leakage.

Having thus described the invention, what is claimed is:

1. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said. head portion having one ormore piston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slightly greater in the thrust axis than in theaxis transverse thereto, one or both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves, and a control element having alower rate of thermal expansion than the piston metal connecting saidthrust faces adjacent said slot or slots.

2. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said head portion having one or morepiston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said.

head portion and the diameter thereof being; slightly greater i thethrust axis than in the axis transverse thereto, one or both of saidthrust faces being separated from said head portion by a horizontal slotor slots located above one of said piston-ring grooves, a controlelement having, a lower rate of. thermal expansion than the piston metalconnecting said thrust faces adjacent said slot or slots, and means forsealing said slot or slots against leakage of the pressure fluid.

3. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said head portion having, one ormore piston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slightly greater in the thrust axis than in theaxis transverse thereto, one or. both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves in the bottom of another of saidgrooves, and a. control element. having a lower rate of thermalexpansion than the piston metal connecting said thrust faces adjacentsaid slot or slots.

4. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said head portion having one or morepiston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slightly greater in the thrust axis than in theaxis transverse thereto, one or both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves in the bottom of another of saidgrooves, a control element having a lower rate of thermal expansion thanthe piston metal connecting said thrust faces adjacent said slot orslots, and means for sealing said slot or slots against the leakage ofthe pressure fluid.

5. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, and'pin bosses below Said head portion, said head portion having one or morepiston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slightly greater in the thrust axis than in theaxis transverse thereto, one or both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves in the bottom of another of saidgrooves, a control element having a lower rate of thermal expansion thanthe piston metal connecting said thrust faces adjacent said slot orslots, and a sealing band in the bottom of said last groove closing saidslot or slots against leakage of the pressure fluid.

6.. A light-metal piston of the character described having a skirtportion formed. to provide opposite thrust faces and having apiston-ring groove adjacent the upper end thereof, the ring land abovesaid groove being dimensioned to contact the cylinder wall; aheadportion having a smaller diameter than said skirt portion and one ormore piston-ring grooves formed therein, wrist-pin bosses spaced belowsaid head portion, one or both of said thrust faces being separated fromsaid: head portion by a horizontal slot or slots, and a control elementhaving a lower rate of thermal expansion than the piston metal conmeeting said thrust faces adjacent said slot or slots.

7.. A light-metal piston of the character described having a skirtportion formed: to provide opposite thrust. faces and having apiston-ring groove adjacent the upper end thereof, the ringland abovesaid groove being. dimensioned to contact the cylinder wall; a headportion having a smaller diameter than said skirt portion and one ormore piston-ring, grooves formed therein,

wrist-pin bosses spaced. below said head portion, one or both of saidthrust faces being separated from said head portion by a horizontal slotor slots in one of said ring grooves, means in. said lastv groove. forsealing saidslot or slots against leakage of. the pressure fluid, and acontrol. element having a lower rate of thermal expansion than thepiston metal, connecting said thrust faces adjacent said slot or slots,

8:. A light-metal piston of. the character (18-- scribed having a skirtportion formed to provide opposite thrust faces and having a piston-ringgroove adjacent the upper end thereof, the ring land above said groovebeing dimensioned to contact the cylinder wall; a head portion having asmaller diameter than said skirt portion and one or more piston-ringgrooves formed therein, wrist-pin bosses spaced below said head portion,one or both of said thrust faces being separated from said head portionby a horizontal slot or slots in one of said ring grooves, a sealingband embracing the piston in said last groove to close said slot orslots against leakage of the pressure fluid, and a control elementhaving a lower rate of thermal expansion than the piston metalconnecting said thrust faces adjacent said slot or slots.

9. A light-metal piston of the character described having a skirtportion formed to provide opposite thrust faces and having a piston-ringgroove adjacent the upper end thereof, the ring land above said groovebeing dimensioned to contact the cylinder wall, a head portion having asmaller diameter than said skirt portion and one or more piston-ringgrooves formed therein, wrist-pin bosses spaced below said head portion,one or both of said thrust faces being separated from said head portionby a horizontal slot or slots in one of said ring grooves, a thinresilient snap-ring in said last groove sealing said slot or slotsagainst leakage of the pressure fluid, and a control element having alower rate of thermal expansion than the piston metal connecting saidthrust faces adjacent said slot or slots.

10. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said head portion having one or morepiston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slightly greater in the thrust axis than in theaxis transverse thereto, one or both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves.

11. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said head portion having one or morepiston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slightly greater in the thrust axis than in theaxis transverse thereto, one or both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves, and means for sealing said slotor slots against leakage of the pressure fluid.

12. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said head portion having one or morepiston-ring grooves therein, said skirt portion having one or morepiston-ring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slightly greater in the thrust axis than in theaxis transverse thereto, one or both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves in the bottom of another of saidgrooves.

13. A light-metal piston of the character described having a headportion, a skirt portion formed to provide opposite thrust faces, andpin bosses below said head portion, said head portion having one or morepiston-ring grooves therein, said skirt portion having one or morepistonring grooves therein near the upper end thereof, said skirtportion having a greater diameter than said head portion and thediameter thereof being slight'y greater in the thrust axis than in theaxis transverse thereto, one or both of said thrust faces beingseparated from said head portion by a horizontal slot or slots locatedabove one of said piston-ring grooves in the bottom of another of saidgrooves, and means for sealing said slot or slots against the leakage ofthe pressure fluid.

14. A light-metal piston of the character described having a skirtportion formed to provide opposite thrust faces and having a piston-ringgroove adjacent the upper end thereof, the ring land above said groovebeing dimensioned to contact the cylinder wall; a head portion having asmaller diameter than said skirt portion and one or more piston-ringgrooves formed therein, wrist-pin bosses spaced below said head portion,one or both of said thrust faces being separated from said head portionby a horizontal slot or slots in one of said ring grooves, and means insaid last groove for sealing said slot or slots against leakage of thepressure fluid.

15. A light-metal piston of the character described having a skirtportion formed to provide opposite thrust faces and having a piston-ringgroove adjacent the upper end thereof, the ring land above said groovebeing dimensioned to contact the cylinder wall; a head portion having asmaller diameter than said skirt portion and one or more piston-ringgrooves formed therein, wrist-pin bosses spaced below said head portion,one or both of said thrust faces being separated from said head portionby a horizontal slot or slots in one of said ring grooves, and a sealingband embracing the piston in said last groove to close said slot orslots against leakage of the pressure fluid.

WILLIAM M. VENNER. PERCY L. BOWSER, JR.

No references cited.

